The present invention relates to a pump assembly of the kind having a single motor for driving a plurality of pumps. Also, the present invention relates to an improvement in a film processor having a plurality of tanks for holding solutions that periodically need to be replenished.
It is known to provide a single motor for driving two or more pumps. One example is a single motor, dual bellows pump Model No. 90885-000 sold by the Gorman Rupp Industries of Belleville, Ohio. Pump assemblies of this kind have two bellows pumps which are driven simultaneously by a single motor. It is known to use such pumps for replenishing solutions in a film processor having a plurality of tanks containing developer and fixer solutions needed for processing film, such as X-ray film. The solutions are depleted during development of film. When the motor is energized the pumps both are operated to simultaneously provide replenishment solutions to each of two tanks. The developer and fixer solutions typically to not need replenishment at the same rates. For example, one solution may need to be replenished 20 percent more than the other solution. Therefore a mechanical adjustment is provided for the bellows pumps which enables one bellows to pump from 0 to 100 percent of the capacity of the other bellows. This adjustment is crude and an inconvenient adjustment for the user. Also, the need for replenishment of the processing solutions is a function of the quantity of film processed in a particular time period and the amount of solution that evaporates from the tank during that time period.
While the replenishment system described above has operated satisfactorily, it suffers some disadvantages. For example, it cannot easily handle the situation where one tank is depleted of solution to an extent requiring replenishment prior to the time the other tank requires replenishment. Under the circumstances, if the motor is operated to replenish the depleted supply in the first tank, the second tank may be excessively replenished, resulting in an inaccurate chemical concentration, or the second tank may be filled beyond its capacity with the excess solution being diverted to a drain. In order to avoid such problems the depleted solution may not be replenished completely. Clearly there is a need to independently provide replenishment solutions to tanks in film processors in order that the precise amount of replenishment fluid can be provided to each tank based on its needs. This could be accomplished by providing two separate independent pumps with different motors, but such unnecessarily increases the cost of the film processor and complicates its controls.